1. Field of the Invention
This invention relates to rocket vehicles and, more particularly, to arrangements for steering such vehicles by controlling thrust direction.
2. Description of Related Art
As military aircraft become faster and more maneuverable, there is increased need for faster and more maneuverable missiles with longer ranges to counter these threats. One method of increasing maneuverability of a missile is to use a steerable nozzle on the rocket motor to allow the direction of thrust to be controlled. This affords greater maneuverability than traditional movable aerodynamic fins alone can provide under low speed or very high altitude conditions when the dynamic pressure is low. The mechanism used to move the steerable nozzle is known as the nozzle actuator system. The nozzle actuator system usually is located around the nozzle and infringes on the volume one would like to fill with rocket fuel. If the overall dimensions of the rocket motor are fixed, the smaller the nozzle actuator, the more room remains for fuel. Thus, smaller nozzle actuators give the missile greater range.
Nozzle actuators and similar steering systems have been built based on hydraulic, pneumatic and electromechanical control systems. For example, Pollak in U.S. Pat. No. 2,850,977 discloses a gimballed power plant in a jet propelled aircraft in which exhaust gases from the rocket propulsion motor are utilized to adjust the rocket motor axis relative to the flight axis of the aircraft by having gyro-operated rotatable fins positioned in the exhaust gas stream. Adjustment of these fins by the aerodynamic forces impinging on them causes movement of the propulsion motor relative to the vehicle axis.
The Tolson U.S. Pat. No. 3,200,587 describes a number of structural arrangements for shifting a rocket engine exhaust nozzle to shift the thrust axis from a position coincidental with the central axis of the vehicle to various positions where it is laterally displaced from the central axis. Movement of the thrust or vehicle axis applies torque to axis from the center of gravity the vehicle to effect directional change.
The Kuhn, Jr. U.S. Pat. No. 3,073,630 discloses a particular design of rocket engine gimbal which is provided to control the body, thrust direction of a rocket engine, relative to a missile by pivoting the exhaust nozzle in the gimbal.
Other schemes using steerable propulsion systems for exhaust jet propulsion systems are disclosed in U.S. Pat. Nos. 3,237,890 of Thielman, 2,919,544 of Smith, Jr. et al, 3,908,908 of Johnson and 3,188,024 of Schneider.
In the development of modern nozzle actuators for controlling steerable exhaust nozzles, electromechanical systems have become dominant because of their improved effectiveness, reliability and reduced weight. Electromechanical nozzle actuators conventionally involve motors and some type of speed reducer to transform the high speed, low torque motor motion into high torque, low speed nozzle motion. This has been accomplished in the past with ball screws or gear reducers and four-bar type linkages. Previously known speed reducers have been bulky and heavy, and thus present certain inherent limitations. Known prior art designs do not present the advantages of the arrangements in accordance with the present invention which are shorter, lighter, easier to fabricate, and better adapted for greater maneuverability of missiles and the like.